Why Mars?

Phoenix Mars Lander is on final approach now. If you could hitch a ride on the little ship, you would see a rusty red globe looming in the distance, slowly growing. Nothing much will happen until late Sunday afternoon, U.S. time, when the ship jettisons its cruise stage, and goes plowing into the Martian atmosphere. Engineers hope that in a seven-minute period, it will slow from 12,700 miles an hour…to only five. (Take a look, if you haven’t already read it, at Gina Sunseri’s piece.) Landing is a risky proposition, and the mission managers at JPL are clearly trying to keep expectations low. A very similar probe, Mars Polar Lander, crashed in 1999. All of which raises the question of why they try. I invite you to weigh in, as we get closer to Sunday, but here’s one answer, from an interview I did a couple of years ago with Steve Squyres, the Cornell astronomer who is the principal investigator for the twin Mars rovers, Spirit and Opportunity. They landed safely on Mars in 2004, and though they’re clearly wearing down, they’re still going. Squyres and his team say the rovers found clear evidence that there was once standing water on the Martian surface — brackish pools and rivulets, thick with the minerals that make the planet red. That water is long gone — but the rovers both landed near the Martian equator. Readings from orbit show there’s still ice in the soil near the Martian poles, which is where Phoenix is headed. It is set to land at 68 degrees north latitude, which, on Earth, would be like landing in northwestern Canada near the Arctic Ocean. Water, plus time, plus organic molecules — those are thought to be good ingredients for the rise of life, and Phoenix is designed to look for organic compounds. But if the mix is right, does life just…happen? Or does there need to be something more? That, to Squyres, is why Mars is worth exploring, and that’s what we discussed down the hall from his office at Cornell. "Life might have originated on Mars. Did it? We don’t know,” he said. But if you can show that life arose independently on two different worlds, just in this one solar system, it takes no great leap of imagination or faith, or anything else, to begin to believe that life might be common throughout the universe." “And the reverse might also be important?” I asked. “The reverse might also be true. You might get to Mars and find that the conditions were once just right for life. It was warm, it was wet, there were pools of water—and you could search for years and find no evidence of life. “That would be important too,” said Squyres. “It means that life is pretty special.”